Printed wiring board and method for manufacturing the same

ABSTRACT

A printed wiring board includes an insulating layer, a first conductor layer embedded into a first surface of the insulating layer and including connecting portions to connect an electronic component, a second conductor layer projecting from a second surface of the insulating layer, a solder resist layer covering the first conductor layer and having an opening structure exposing the connecting portions, a barrier metal layer formed on the connecting portions such that the barrier layer is projecting from the first surface of the insulating layer, and metal posts formed on the barrier layer such that the metal posts are positioned on the connecting portions, respectively. Each metal post has width which is greater than width of a respective connecting portion, and the barrier metal layer includes a metal material which is different from a metal material forming the metal posts and a metal material forming the first conductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims the benefit of priorityto Japanese Patent Application No. 2014-161617, filed Aug. 7, 2014, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printed wiring board on which anelectronic component is mounted and to a method for manufacturing theprinted wiring board. More specifically, the present invention relatesto a printed wiring board having a structure that allows certainty andreliability of connection between an electronic component and theprinted wiring board to be improved and in which patterning of metalposts can be reliably performed and over etching of a wiring pattern canbe avoided, and to a method for manufacturing the printed wiring board.

2. Description of Background Art

Japanese Patent Laid-Open Publication No. HEI 10-173316 describes astructure in which a resin film, on which a conductor circuit pattern isformed, is press-bonded to an insulating substrate and thereafter, bypeeling off the resin film, the conductor circuit pattern is embedded inthe insulating substrate. The entire contents of this publication areincorporated herein by reference.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a printed wiring boardincludes a resin insulating layer, a first conductor layer embedded intoa first surface of the resin insulating layer and including connectingportions positioned to connect an electronic component, a secondconductor layer projecting from a second surface of the resin insulatinglayer on the opposite side of the resin insulating layer with respect tothe first surface, a solder resist layer formed on the first surface ofthe resin insulating layer such that the solder resist layer is coveringthe first conductor layer and has an opening structure exposing theconnecting portions of the first conductor layer, a barrier metal layerformed on the connecting portions of the first conductor layer such thatthe barrier layer is projecting from the first surface of the resininsulating layer, and metal posts formed on the barrier layer such thatthe metal posts are positioned on the connecting portions of the firstconductor layer, respectively. The metal posts are formed such that eachof the metal posts has a width which is greater than a width of arespective one of the connecting portions, and the barrier metal layerincludes a metal material which is different from a metal materialforming the metal posts and a metal material forming the first conductorlayer.

According to another aspect of the present invention, a method formanufacturing a printed wiring board includes laminating a metal film ona carrier including a carrier metal layer such that the metal film islaminated on a surface of the carrier metal layer, forming a barriermetal layer on an entire surface of the metal film such that the barriermetal layer includes a metal material which is different from a metalmaterial forming the metal film, forming a first conductor layer on thebarrier metal layer such that the first conductor layer includes a metalmaterial which is different from the metal material forming the barriermetal layer and includes connecting portions positioned to connect anelectronic component, forming a resin insulating layer on the firstconductor layer such that the first conductor layer is embedded into afirst surface of the resin insulating layer, forming a second conductorlayer on a second surface of the resin insulating layer on the oppositeside of the resin insulating layer with respect to the first layer,removing the carrier from the metal film such that a surface of themetal film is exposed, etching the metal film such that metal posts areformed on the connecting portions of the first conductor layer,respectively, and each of the metal posts has a width which is greaterthan a width of a respective one of the connecting portions, etching thebarrier metal layer such that the barrier metal layer includes portionsformed between the metal posts and the connecting portions,respectively, and forming a solder resist layer on the first surface ofthe resin insulating layer such that the solder resist layer covers thefirst conductor layer and has an opening structure exposing the metalposts.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an explanatory cross-sectional view of a printed wiring boardaccording to an embodiment of the present invention;

FIG. 2 is an explanatory cross-sectional view of a printed wiring boardaccording to another embodiment of the present invention;

FIG. 3 is an explanatory cross-sectional view of a printed wiring boardaccording to yet another embodiment of the present invention;

FIG. 4A is an enlarged explanatory cross-sectional view for describing ashape of a metal post, in which a dimension in a thickness direction isexaggerated;

FIG. 4B is an enlarged explanatory cross-sectional view for describing ashape of a metal post, in which a dimension in a thickness direction isexaggerated;

FIG. 5A is an explanatory plan view of the printed wiring boardillustrated in FIG. 1;

FIG. 5B is an explanatory plan view of the printed wiring boardillustrated in FIG. 2;

FIG. 5C is an explanatory plan view illustrating another embodiment of awiring pattern illustrated in FIG. 3;

FIG. 6A is an explanatory cross-sectional view illustrating a process ofa method for manufacturing the printed wiring board illustrated in FIG.1;

FIG. 6B is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6C is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6D is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6E is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6F is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6G is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6H is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1;

FIG. 6I is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1; and

FIG. 6J is an explanatory cross-sectional view illustrating a process ofthe method for manufacturing the printed wiring board illustrated inFIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings. FIG. 1 is anexplanatory cross-sectional view of a printed wiring board 1 of thepresent embodiment (FIG. 1 illustrates a cross section along an I-I linein FIG. 5A; however, for simplicity, the number of wirings is reduced).In printed wiring board 1 of the present embodiment, a first conductorlayer 12 is provided that is embedded on a first surface (11 a) side ofa resin insulating layer 11 that has the first surface (11 a) and asecond surface (11 b) that is on an opposite side of the first surface(11 a). The first conductor layer 12 includes multiple connectingportions (12 b) to which an electronic component (not illustrated in thedrawings) is electrically connected. A second conductor layer 14 isformed projecting from the second surface (11 b) of the resin insulatinglayer 11. Further, a via conductor 15 is formed that penetrates throughthe resin insulating layer 11 and electrically connects the firstconductor layer 12 and the second conductor layer 14. A solder resistlayer 16 is formed on the first surface (11 a) of the resin insulatinglayer 11 and on the first conductor layer 12. An opening (16 a) isformed in the solder resist layer 16 for exposing the respectiveconnecting portions (12 b) of multiple wirings (12 a) of the firstconductor layer 12 that connect to the electronic component. Metal posts13 are respectively provided via a barrier metal layer 17 on theconnecting portions (12 b) that are exposed from the opening (16 a). Themetal posts 13 are formed by keeping portions of a metal film (13 a)(see FIG. 6H) and removing other portions by etching such that the metalposts 13 has a width (w1) larger than a width (w2) of the wirings (12 a)of the connecting portions (12 b). The barrier metal layer 17 is made ofa metal different from those of the metal posts 13 and the firstconductor layer 12, and is formed projecting from the first surface (11a) of the resin insulating layer 11.

That is, as illustrated in FIGS. 1 and 5A, the wirings (12 a) arearranged side by side, and are embedded in the resin insulating layer 11so that only one surface of each of the wirings (12 a) is exposed. Asillustrated in FIG. 1, 2, 5A and 5B, the connecting portions (12 b) ofthe wirings (12 a) may be formed to be arranged in one row along aarrangement direction of adjacent wirings (12 a). As illustrated inFIGS. 3 and 5C, the connecting portions (12 b) of the wirings (12 a) mayalso be formed at positions that are shifted at a constant pitch betweenadjacent wirings (12 a) and arranged in a so-called zigzag pattern. Whenan interval between the wirings (12 a) is narrow, that the connectingportions (12 b) are formed in the zigzag pattern as illustrated in FIG.5C is preferable in that contact between adjacent wirings (12 a) can beavoided. In other words, as illustrated in FIG. 5A-5B, when theconnecting portions (12 b) are arranged in one row, the connectingportions (12 b) are aligned in one row; and as illustrated in FIG. 5C,when the connecting portions (12 b) are formed at the positions that areshifted at a constant pitch between adjacent wirings (12 a), theconnecting portions (12 b) are aligned in two rows. When the connectingportions (12 b) are formed in the zigzag pattern, it is also possiblethat one opening (16 a) is formed in the solder resist layer 16 for eachof the connecting portions (12 b).

In all the embodiments of FIG. 1-3, the first conductor layer 12 isformed to be embedded in the resin insulating layer 11, and the metalposts 13 are formed on a surface of the first conductor layer 12 via thebarrier metal layer 17. The barrier metal layer 17 is formed of amaterial different from those of the metal post 13 and the firstconductor layer 12. That is, the metal posts 13 (see FIG. 6I) are formedby patterning the metal film (13 a) (see FIG. 6H) on the first conductorlayer 12. Therefore, when the first conductor layer 12 and the metalfilm (13 a) are formed of the same material such as copper, a boundarybetween the two for etching is not clear. Then, a problem occurs that,when etching is performed until the metal film (13 a) that is notcovered by a mask is completely removed in order to prevent shortcircuiting between the wirings (12 a), the first conductor layer 12 isover etched and the wirings (12 a) become thin. However, as in thepresent embodiment, when the barrier metal layer 17 is interposedbetween the first conductor layer 12 and the metal film (13 a), theboundary between the two is clearly defined and over etching of thefirst conductor layer 12 is prevented. An etching solution for thebarrier metal layer 17 and an etching solution for the metal posts 13and the first conductor layer 12 are different from each other.Therefore, the barrier metal layer 17 may be formed to be a very thinfilm having a thickness of about a few micrometers (pm) or less. Forexample, the barrier metal layer 17 is formed of a nickel film, atitanium film, or the like. In the examples illustrated in FIG. 1-3, thebarrier metal layer 17 is formed to have a width larger than the width(w1) of each of the metal posts 13. However, it is not necessary thatthe barrier metal layer 17 is larger than each of the metal posts 13. Aprojected area of each of the metal posts 13 and a projected area of thebarrier metal layer 17 may be the same in size. When the barrier metallayer 17 is formed to have the same pattern as the metal posts, thebarrier metal layer 17 can be patterned without particularly providing amask. In any case, the pattern of the barrier metal layer 17 has a sizelarger than the width of the wiring (12 a).

In a high-frequency circuit or the like, due to the skin effect, currentflows only near a surface. Therefore, it is desirable that a coatinghaving a large electrical resistance be not formed on a surface of thebarrier metal layer 17. From this point of view, it is preferable thatthe barrier metal layer 17 that is exposed on the surface be removed asmuch as possible. However, the barrier metal layer 17 is only interposedin areas of the connecting portions (12 b) and thus is not causing aproblem. As will be described later in a manufacturing method, a metalcoating (electroless plating film) that is formed after formation of abarrier metal film (17 a) is also removed by etching after the formationof the first conductor layer 12 except a portion on a lower side of thefirst conductor layer 12.

Further, in all the examples illustrated in FIG. 1-3, the metal posts 13are formed by patterning the metal film (13 a) such that the width (w1)of the metal posts 13 is larger than the width (w2) of the wirings (12a) of the connecting portions (12 b). In this way, the metal posts 13are formed to have the width (w1) larger than the width (w2) of thewirings (12 a) of the connecting portions (12 b). Thereby, even when thewirings (12 a) are narrow, a portion of each of the wirings thatconnects to an electronic component can be formed to have a large width,and thus it does not cause a problem in connecting to an electroniccomponent or the like. That is, the connecting portions (12 b) can eachbe formed to have a large area and the metal posts 13 can each be formedto have a certain height. Thereby, the metal posts 13 are formed on thefirst surface of the resin insulating layer 11, not embedded in theresin insulating layer 11. Therefore, even for thermal expansion andthermal contraction, a stress can be easily absorbed. Therefore, forexample, when an electronic component is mounted, even when warpageoccurs in the printed wiring board, it is relatively easy to reliablyconnect the electronic component. Further, a stress due to thermalexpansion and thermal contraction due to heat cycles after the printedwiring board is incorporated in a set is easily absorbed. It is alsopossible that only portions of the wirings (12 a) on the lower side ofthe metal posts 13 are formed wide. When the portions of the wirings (12a) on the lower side of the metal posts 13 are formed wide, contactportions between the wirings (12 a) and the metal posts 13 can each beensured with a sufficient area, and stable connection can be obtained.

In the present embodiment, as described above, the metal posts 13 havingthe width (w1) larger than the width (w2) of the wirings (12 a) arerespectively formed on the wirings (12 a). An electronic component orthe like is connected to the metal posts 13 that are formed to have alarge size. Therefore, the connecting portions (12 b) of the wirings (12a) and the electronic component or the like can be reliably connected.In addition, the metal posts 13 are formed to have a high height of 10μm or more. Therefore, even when the electronic component or the likeand the resin insulating layer 11 have different thermal expansioncoefficients, a thermal stress can be easily absorbed by the metal posts13, and connection strength and reliability can be further improved. Inparticular, the metal posts 13 are each formed in a curved shape that isthick on a bottom surface side (the wiring (12 a) side) and is narrow onan upper surface side (opposite side of the bottom surface side).Thereby, a stress can be more easily absorbed, and an area of a portionsoldered to the electronic component or the like can be reduced whilethe connection to the wirings (12 a) can be sufficiently performed.Therefore, a risk of occurrence of contact can be further suppressed. Asa result, very highly reliable electrical connection to the electroniccomponent or the like can be achieved.

Further, the size of the pattern of the metal posts can be easilyadjusted by a patterning mask. Therefore, in a case such that wherewarpage occurs in the resin insulating layer when temperature risesduring solder reflow during mounting, by adjusting the size of the metalposts, a height of solder bumps or the like can be adjusted and aconnection failure or the like due to the warpage during mounting can beprevented.

Further, as described in a manufacturing method (to be described later),the metal posts 13 may be a metal film which is on a carrier inmanufacturing a printed wiring board and which is eventually discarded.That is, using a lightly thicker metal film than one discarded, bypatterning and letting portions of the metal film remain, the metalposts 13 may be formed. Therefore, there is substantially no increase inmaterial and there is also no significant increase in processes. In theexample illustrated in FIG. 5C, every other ones of the positions of theconnecting portions (12 b) are shifted. Therefore, for example, in FIG.3 that illustrates a cross-sectional view along a line in FIG. 5C, in aportion that is not a connecting portion, a cross section of the solderresist layer 16 is visible, and a metal post 13 is hidden behind thecross section.

The embodiments illustrated in FIG. 1-3 are common in a basic relationbetween sizes of the metal posts 13 and the wirings (12 a) and in thatthe barrier metal layer 17 is interposed between the metal posts 13 andthe first conductor layer 12. On the other hand,

FIG. 1-3 are different in that the shape of the opening (16 a) of thesolder resist layer 16 is different in each case, and in that, in thestructure illustrated in FIG. 3, as illustrated in FIG. 5C, theconnecting portions of adjacent wirings (12 a) are formed at positionsthat are shifted at a constant pitch, and are arranged in two rows;however, other structures are substantially the same. As describedabove, with regard to the pattern of the opening of the solder resistlayer 16 (arranged in one row or in a zigzag pattern) and to the coatingof the solder resist layer 16 (whether a portion of each of the metalposts 13 is covered or only a surrounding area is covered, or whetherthe opening is a large collective opening, these structures can beindependently adopted, and are not limited to the structures illustratedin the drawings.

In the structure of the embodiment illustrated in FIG. 1, as illustratedin FIG. 5A, the opening is formed as a collective opening such that theconnecting portions (12 b) are arranged in one row and are entirelyexposed. When the interval between the wirings is narrow, a risk ofcontact between the wirings is high. However, when there is a certaininterval between the wirings (12 a), forming such a collective openingallows a manufacturing process to be simplified. In the embodimentillustrated in FIG. 2, as illustrated in the explanatory plan view ofFIG. 5B, the connecting portions (12 b) similar to those of FIG. 1 areformed. However, the solder resist layer 16 is formed also insurrounding areas of the metal posts 13, and the openings (16 a) areformed such that the metal posts 13 are entirely exposed. When such asolder resist layer 16 is formed, a contact incident between adjacentwirings (12 a) can be prevented and thus it is preferable.

FIG. 3 illustrates a cross-sectional view along a line in FIG. 5C (alsofor this figure, the number of the wirings (12 a) in FIG. 3 does notmatch that in FIG. 5C). As is apparent from FIGS. 3 and 5C, it is not astructure in which the connecting portions (12 b) are arranged in onerow as illustrated in FIGS. 1 and 2, but a structure in which theconnecting portions (12 b) are arranged in a zigzag pattern. Theopenings (16 a) of the solder resist layer 16 are individually formedfor the connecting portions (12 b) and the openings (16 a) are formedsuch that a peripheral portion of each of the metal posts 13 is alsocovered by the solder resist layer 16. That is, as illustrated in FIG.3, a metal post 13 appears for every other one of the wirings (12 a),and a metal post 13 is hidden on a back side of the solder resist layer16 between a pair of adjacent metal posts 13. Therefore, even when theinterval between the wirings (12 a) is narrow, there is no risk ofcontact between them, and electrodes of an electronic component or thelike can be easily connected using the wide metal posts 13. In theexample illustrated in FIG. 3, the connecting portions (12 b) of thewirings (12 a) are formed in a zigzag pattern. Therefore, in the crosssection along the line of FIG. 5C, a cross section of a metal post 13appears only for every other one of the wirings (12 a) in thecross-sectional view. The resin insulating layer 11 is an insulatinglayer that has the first surface (11 a) and the second surface (11 b)that is on the opposite side of the first surface (11 a). The resininsulating layer 11, for example, may be formed by impregnating a corematerial such as glass fiber with a resin composition that contains afiller, and may also be formed using a resin composition alone thatcontains a filler. Further, the resin insulating layer 11 may be formedto be a single layer and may also be formed from multiple insulatinglayers.

When the resin insulating layer 11 is formed from multiple insulatinglayers, for example, a thermal expansion coefficient, flexibility and athickness of the resin insulating layer 11 can be easily adjusted.Examples of the resin include epoxy and the like. The thickness of theresin insulating layer 11, for example, is in a range of 25-100 μm. Thefirst conductor layer 12 is exposed on the first surface (11 a). Thesolder resist layer 16 is formed on the wirings (12 a) other than theconnecting portions (12 b) on which an electronic component is mountedand on the first surface (11 a) of the resin insulating layer 11surrounding the wirings (12 a) such that portions of the wirings (12 a)on which the electronic component is mounted are exposed from theopenings (16 a) of the solder resist layer 16. On the second surface (11b) of the resin insulating layer 11, the second conductor layer 14 (tobe described later) is formed projecting from the second surface (11 b).

The first conductor layer 12 is a pattern of the wirings (12 a) that areembedded on the first surface (11 a) side of the resin insulating layer11. One surface of the embedded first conductor layer 12 is exposedsubstantially flush with the first surface (11 a) of the resininsulating layer 11. In this way, embedding the first conductor layer 12in the resin insulating layer 11 contributes to reduction in a thicknessof the printed wiring board 1 and contributes to improvement in adhesionbetween the first conductor layer and the resin insulating layer 11.Further, it also has an advantage of being able to adapt to fine wiring.On the other hand, as will be described later, when a non-uniform solderresist layer 16 is formed on the first surface (11 a) and on the secondsurface (11 b), there is a problem that warpage is likely to occur inthe resin insulating layer 11. However, in the present embodiment, animpact due to the warpage on connection reliability of an electroniccomponent or the like is reduced. Further, examples of the electroniccomponent include semiconductor elements such as a discrete device andan IC. A method for forming the first conductor layer 12 is notparticularly limited. Preferably, the first conductor layer 12 may be anelectroplating film formed by electroplating. When the first conductorlayer 12 is an electroplating film, there is an advantage that the firstconductor layer 12 is formed as a pure metal film. Copper is an exampleof a material of which the first conductor layer 12 is formed. Copperallows electroplating to be easily performed and has a small electricalresistance, and a corrosion problem is also unlikely to occur. The firstconductor layer 12 has a thickness, for example, in a range of 3-20 μm.

When an interval between the wirings (12 a) is narrow and the metalposts 13 are formed large, there is a possibility that contact betweenadjacent wirings (12 a) may occur. In such a case, from a point of viewof preventing a contact incident, it is preferable that wiring portionsthat are respectively positioned between the connecting portions (12 b)of the wirings (12 a) (the connecting portions (12 b) being arranged inthe zigzag pattern) be formed thin. The wiring portions (12 s) that areformed thin are each formed to have a width of about ⅔-½ of the normalwidth of the wirings (12 a). Even when the wirings (12 a) are somewhatthin, since the wirings (12 a) are embedded in the resin insulatinglayer 11, there is no risk of disconnection and a risk of contactbetween the wirings can be avoided.

The metal posts 13 are respectively formed on the connecting portions(12 b) of the wirings (12 a) that are formed in the first conductorlayer 12, the connecting portions (12 b) being exposed in the openings(16 a) of the solder resist layer 16, and an electronic component beingmounted on the connecting portions (12 b). The metal posts 13 are formedto have the width (w1) that is larger than the width (w2) of the wirings(12 a) at the connecting portions (12 b) on which the metal posts 13 areformed. That is, the wirings (12 a) of the printed wiring board 1 arefine-pitched and the wirings (12 a) are each formed thin. In addition,the interval between the wirings (12 a) is narrow. However, the metalposts 13 are respectively formed to be larger than the wirings (12 a).Therefore, even in the case where an electronic component or the like ismounted on the metal posts 13, connection to the electronic component orthe like can be easily performed. For example, the width (w1) of each ofthe metal posts 13 is about 20 μm; and the width (w2) of each of thewirings (12 a) is about 10 μm. Further, an interval (w3) betweenadjacent wirings (12 a) is about 10 μm. Therefore, an interval betweenan edge of a metal post 13 and an adjacent wiring (12 a) is about 5 μm,which is very narrow. However, for example, as illustrated in FIG. 5C,when the connecting portions (12 b) are formed at the positions that areshifted at a constant pitch between adjacent wirings (12 a), theconnecting portions (12 b) can be easily formed to be exposed withoutcausing contact between adjacent wirings (12 a).

Each of the metal posts 13 may be formed to be a single layer and mayalso be formed from multiple layers. When each of the metal posts 13 isformed from multiple layers, examples of the layers include Cu/Ni,Cu/Ti, Au/Pd/Ni, and Au/Ni. Ni or Ti that is provided as an outermostlayer can function as a surface protection film.

The metal posts 13 may each have a height (thickness) that allowswarpage in the resin insulating layer 11 to be relaxed when anelectronic component is mounted, the warpage being due to rise and fallof temperature when the printed wiring board is incorporated in anelectronic device and is used. That is, when the connecting portions (12b) to which an electronic component is connected are formed only by thefirst conductor layer 12, a large portion excluding the surface of thefirst conductor layer 12 is covered by the resin insulating layer 11.Therefore, when warpage occurs in the printed wiring board 1 due toimbalance of the solder resist layers 16 on the first surface (11 a) andthe second surface (11 b) of the resin insulating layer 11, a stress dueto a difference in thermal expansion coefficient acts only on asoldering portion of the electronic component, and there is a risk thatthe soldering portion becomes unable to withstand the stress and isdamaged. However, the metal posts 13 are provided. Thereby, theperiphery of each of the metal posts 13 are in contact with an openspace, and thus the stress can be easily absorbed by expansion andcontraction of the metal posts 13. The height of the metal posts 13 is,for example, preferably 10-20 μm, and more preferably about 18 μm. Thatthe height of the metal posts 13 is larger than the thickness of thesolder resist layer 16 is preferable in that thickness reduction can beachieved while a stress can be relaxed.

A stress is easily absorbed not only by increasing the height of themetal posts 13 but also by devising the shape of the metal posts 13. Forexample, as depicted in enlarged views illustrated in FIG. 4A and 4B inwhich the thickness of the metal posts 13 is exaggerated, a stress iseasily absorbed by forming the metal posts 13 to have a shape in which aside surface of each of the metal posts 13 is curved.

That is, in a structure illustrated in FIG. 4A, a metal post 13 has anupper surface (UF), a lower surface (BF) on an opposite side of theupper surface, and a side surface (SF) between the upper surface and thelower surface. The side surface (SF) is curved. It is preferable that adiameter (d0) of the metal post 13 at the upper surface (UF) be smallerthan a diameter (d2) of the metal post 13 at the lower surface (BF). InFIG. 4A, a thinnest portion (NP) exists between the upper surface (UF)and the lower surface (BF), and a diameter (d1) of the thinnest portion(NP) is smaller than the diameter (d0) at the upper surface (UF) and issmaller than the diameter (d2) at the lower surface (BF).

In the example illustrated in FIG. 4B, the diameter of the metal post 13increases from the upper surface (UF) toward the lower surface (BF). InFIG. 4B, the thinnest portion (NP) is formed at the upper surface (UF)of the metal post 13, and thus d1=d0.

The shape of the side surface of each of the metal posts 13 is notstraight but curved. Therefore, a stress caused by a difference inphysical properties between the printed wiring board 1 and an electroniccomponent or the like mounted on the printed wiring board is relaxed bythe metal posts 13. Examples of the physical properties include thermalexpansion coefficient, Young's modulus, and the like. The shape of FIG.4A is more suitable for stress relaxation than the shape of FIG. 4B.Such shapes can be obtained by adjusting an etching condition or thelike. Therefore, by controlling the thickness and the shape of the metalposts 13, a stress is further relaxed.

As described above, the barrier metal layer 17 is formed of a materialdifferent from those of the metal posts 13 and the first conductor layer12. Examples of the material include nickel, titanium and the like. Thebarrier metal layer 17 functions as a barrier layer so that, when themetal posts 13 are patterned and formed from the metal film (13 a), thefirst conductor layer 12 that is normally formed of the same material asthat of the metal posts 13 is not etched. In particular, as will bedescribed later, when the metal posts 23 become thick, it is difficultto precisely perform etching control. However, by providing the barriermetal layer 17, the metal posts 13 are accurately formed without anyrisk of over etching the first conductor layer 12. It is sufficient forthe barrier metal layer 17 to have a thickness of about a fewmicrometers (μm).

The second conductor layer 14 is formed projecting from the secondsurface (11 b) of the resin insulating layer 11. A method for formingthe second conductor layer 14 is not particularly limited. Copper is anexample of a material of which the second conductor layer 14 is formed.The second conductor layer 14 has a thickness, for example, in a rangeof 3-20 μm. The second conductor layer 14 is illustrated as an exampleof a single layer in FIG. 1. However, as will be described later, forexample, the second conductor layer 14 may also be formed by a metalfoil and a plating film.

The via conductor 15 penetrates through the resin insulating layer 11and electrically connects the first conductor layer 12 and the secondconductor layer 14. The via conductor 15 is formed by filling aconductor in a through hole (11 d) that penetrates through the secondconductor layer 14 and the resin insulating layer 11. As a material forthe via conductor 15, copper is used as an example. The via conductor 15is formed, for example, by electroplating. The solder resist layer 16 isformed on the first conductor layer 12 and on the first surface (11 a)of the resin insulating layer 11 in a range excluding the wirings (12 a)of the first conductor layer 12 on which electrodes of an electroniccomponent are connected. In the example illustrated in FIG. 1, thesolder resist layer 16 is not formed in an entire region of the wirings(12 a), but is formed in an entire surrounding region excluding a rangeof the opening (16 a). In the example illustrated in FIG. 1, the opening(16 a) is formed as a collective opening that is formed such that theconnecting portions (12 b) of the wirings (12 a) are arranged in a rowand are exposed. However, as illustrated in the above-described FIGS. 2and 3, it is also possible to form separate openings. Further, a secondopening (16 b) is formed so that a C4 pad 20 is exposed. An example of amaterial of which the solder resist layer 16 is formed is thermosettingepoxy resin. The solder resist layer 16 is formed to have a thicknessof, for example, about 20 μm.

As described above, according to the present embodiment, the metal posts13 are provided on the first conductor layer 12 on which an electroniccomponent is mounted. Therefore, even when warpage occurs in the resininsulating layer 11, when the occurrence of the warpage can bepredicted, the pattern of the metal posts 13 can be increased or reducedin size. For wirings (12 a) of which an interval is increased due to thewarpage, it is also possible that the size of the metal posts 13 isreduced and rise of the metal posts 13 is increased. By devising thisway, a connection failure can be avoided. Further, without beingembedded in the resin insulating layer 11, the metal posts 13 projectfrom the surface of the resin insulating layer 11. Therefore, the metalposts 13 can easily adapt to expansion and contraction and thus canfunction as a relaxation layer that absorbs a stress. Therefore, notonly yield reduction due to connection failure during mounting isprevented, but also occurrence of cracking or the like due to heatcycles after use is prevented and the reliability is significantlyimproved.

Next, a manufacturing method of the embodiment illustrated in FIG. 1 isdescribed. Manufacturing processes are the same also for the embodimentsof FIGS. 2 and 3 except that the patterning of the opening of the solderresist layer 16 is different.

First, as illustrated in FIG. 6A, a carrier 18 is prepared on which themetal film (13 a) is provided. As the carrier 18, for example, acopper-clad laminated plate is used. However, the present invention isnot limited to this. In the example illustrated in FIG. 1, for example,the metal film (13 a) with a carrier copper foil (18 b) is affixed usingan adhesive or using a thermal compression bonding method or the like toboth sides of a support plate (18 a) that is formed of, for example, aprepreg. Thereby, on both sides of the support plate (18 a), forexample, the carrier copper foil (18 b) is affixed and the carrier 18 isformed. For example, the metal film (13 a) is formed to have a thicknessof 5-20 μm and preferably 10-20 μm, and the carrier copper foil (18 b)is formed to have a thickness of 15-30 μm and preferably about 18 μm.

The carrier 18 is used as a substrate during processing of the followingprocesses and, as will be described later, will be removed without beingleft as a printed wiring board. Therefore, in order for the carrier 18to be separated from the first conductor layer 12 and the like, themetal film (13 a) is provided on the surface of the carrier 18. However,the metal film (13 a) is bonded to or fixed on the carrier 18 over theentire surface via an easily separable adhesive such as a thermoplasticresin or the like interposed between the metal film (13 a) and thecarrier 18 so that the metal film (13 a) is easily separable from thecarrier 18. That is, the carrier copper foil (18 b) and the metal film(13 a) are bonded over the entire surface by a thermoplastic resin orthe like to form the metal film (13 a) with the carrier copper foil (18b), and the carrier copper foil (18 b) is bonded to the support plate(18 a) by thermal compression bonding or the like. By being bonded bythe thermoplastic resin, even when being bonded over the entire surface,the metal film (13 a) and the carrier copper foil (18 b) can be easilyseparated from each other due to a temperature rise. However, withoutbeing limited to this, for example, it is also possible that the metalfilm (13 a) and the carrier copper foil (18 b) are bonded or fixed toeach other over only a surrounding area. By being fixed to each otherover the surrounding area, the two can be easily separated from eachother by cutting the surrounding area. Therefore, the fixation in thesurrounding area in this case is not limited to using the thermoplasticresin. It is desirable that there be no difference in thermal expansionand the like between the carrier 18 and the metal film (13 a).Therefore, when nickel is used for the metal film (13 a), it ispreferable that the carrier copper foil is also formed of the samematerial such as a carrier nickel foil. Therefore, a release layer maybe suitably provided on the surface of the carrier 18 on which the metalfilm (13 a) is provided.

In the example illustrated in FIG. 6A, the metal film (13 a) with thecarrier copper foil, which is obtained by bonding the carrier copperfoil (18 b) and the metal film (13 a) in advance using an adhesive orthe like, is affixed to the support plate (18 a). However, it is alsopossible that the metal film (13 a) is bonded over the entire surface orin the surrounding area or the like to the carrier 18 that is obtainedby affixing the carrier copper foil (18 b) or the like to the supportplate (18 a). Further, an example is illustrated in which the metal film(13 a) is provided on both sides of the carrier 18. This is preferablein that two printed wiring boards are manufactured at once utilizingboth sides of the carrier 18 that is to be discarded. However, it isalso possible that only one side of the carrier 18 is used, or differentcircuit patterns are formed on the two sides. In an example describedbelow, the same circuit pattern is formed on the both sides. Therefore,although both sides are illustrated in the drawings, only one side isdescribed, and, with regard to the other side, reference numerals anddescription are partially omitted.

As illustrated in FIG. 6B, a barrier metal film (17 a) is formed on asurface of the metal film (13 a), and a metal coating (12 f) is furtherformed on a surface of the barrier metal film (17 a). As describedabove, the barrier metal film (17 a) is for preventing the firstconductor layer under the metal film (13 a) from being over etched andthe wirings (12 a) from becoming too thin even when the metal film (13a) vanishes when the metal film (13 a) is etched and patterned. Thebarrier metal film (17 a) is formed of a material different from thoseof the metal film (13 a) and the first conductor layer 12. For example,a copper material may be used for the metal film (13 a) and the firstconductor layer 12.

Therefore, it is preferable that a nickel or titanium film be used asthe barrier metal film (17 a), and the barrier metal film (17 a) beformed using an electroplating method. The nickel film is easilyoxidized. Therefore, it is preferable that a thin metal coating beformed, for example, by electroless plating after the nickel film (17 a)is formed so that a resistive component is not incorporated as much aspossible into the nickel film. The metal coating (12 f) is formed sothat a surface is kept clean and an oxide film is not formed. It ispreferable that a film such as a copper coating that is stable and has asmall electrical resistance be formed using other methods such as vacuumdeposition. For example, by forming a copper coating, electroplating iseasily performed using the metal coating as a seed layer. The metalcoating (12 f) is not required. However, as described above, the nickelplating film (17 a) is easily oxidized. Therefore, it is preferable thata stable metal coating (12 f) be formed on the surface of the nickelplating film using an electroless plating method or vacuum deposition.

As illustrated in FIG. 6C, electroplating is performed using the metalcoating (12 f) as one of electrodes. That is, the first conductor layer12 is formed that includes the wirings (12 a) and the like on which anelectronic component is mounted. A method for forming the firstconductor layer 12 is as follows. A resist pattern (not illustrated inthe drawings) for forming a predetermined pattern is formed on thesurface of the metal coating (12 f). For example, copper plating isperformed on a portion where the metal coating (12 f) is exposed usingan electrolytic copper plating method using the metal film (13 a) or themetal coating (12 f) as one of the electrodes. Thereby, the firstconductor layer 12 is formed. Thereafter, by removing the resistpattern, the first conductor layer 12 is formed on the barrier metalfilm (17 a) via the metal coating (12 f) as illustrated in FIG. 6C.

As illustrated in FIG. 6D, the resist pattern is removed, and the metalcoating (12 f) that is formed from electroless plating and the like andis exposed is removed by etching. The metal coating (12 f) is very thin,and thus is removed by subjecting the entire surface to light etchingwithout masking the surface of the first conductor layer 12. As aresult, the metal coating (12 f) remains only between the barrier metalfilm (17 a) and the first conductor layer 12, and is removed in otherplaces.

As illustrated in FIG. 6E, the resin insulating layer 11 and a metalfoil (14 a) that becomes a part of the second conductor layer 14 arelaminated on the first conductor layer 12 and on the surface of thebarrier metal film (17 a) that is exposed. For the lamination of theresin insulating layer 11 and the metal foil (14 a), a method may beused, in which bonding is performed by applying pressure and heat.

Next, the through hole (11 d) is formed. As a method for forming thethrough hole (11 d), a method of laser irradiation is used. That is, thethrough hole (11 d) is formed at a portion where the first conductorlayer 12 and the second conductor layer 14 that are provided on the twosides of the resin insulating layer 11 are connected, and is processedby irradiating CO2 laser or the like from the surface of the metal foil(14 a).

Next, a metal coating such as an electroless plating film or the like(not illustrated in the drawings) is formed in the through hole (11 d)and on the metal foil (14 a). Next, as illustrated in FIG. 6F, forexample, by electroplating, the via conductor 15 is formed, and a layerof a metal coating (not illustrated in the drawings) and anelectroplating film (14 b) is formed on the surface of the metal foil(14 a). The second conductor layer 14 is formed by the metal foil (14 a)and the metal coating (not illustrated in the drawings) and theelectroplating film (14 b). Then, the metal coating (not illustrated inthe drawings) and the metal foil (14 a) are patterned and the secondconductor layer 14 that includes three layers is formed, and this stateis illustrated in FIG. 6F. The formation of the second conductor layer14 by patterning is performed by forming a normal resist film,patterning and etching.

As illustrated in FIG. 6G, the carrier 18 is removed. In FIG. 6G, forclarity of the description, only the upper side of the carrier 18illustrated in FIG. 6F is illustrated with up and down being inverted inthe drawing. As described above, the carrier 18 (carrier copper foil (18b)) and the metal film (13 a) are fixed to each other by an easilyseparable adhesive or the like such as a thermoplastic resin, and thuscan be easily separated from each other by peeling one from the other ina state in which the temperature has been raised, and a surface of themetal film (13 a) that is in contact with the carrier copper foil (18 b)is exposed.

As illustrated in FIG. 6H-6J, the metal film (13 a) is patterned, andthe metal posts 13 are formed (see FIG. 6J). As illustrated in FIG. 6H,the patterning of the metal posts 13 is performed such that the metalposts 13 are formed on the surfaces of the connecting portions (12 b) ofthe wirings (12 a) of the first conductor layer 12 (see FIG. 5A) via thebarrier metal layer 17 in an example illustrated in FIG. 6J. Forexample, a mask 19 that is made of a solder plating film is patternedand formed. A portion exposed from the mask 19 that is made of thesolder plating film is etched. Thereby, the metal posts 13 are formed ina predetermined patterned (See FIG. 6I). In doing so, a side of each ofthe metal posts 13 is slightly smaller than a width of the mask 19 thatis made of the solder plating film. However, the etching stops on thefirst conductor layer 12 side due to the barrier metal film (17 a) (seeFIG. 6H) that is formed on the surface of the first conductor layer 12.Thereafter, using an etching solution that can selectively etch only thebarrier metal film (17 a), the metal film (13 a) is removed and theexposed barrier metal film (17 a) is selectively etched. As a result,the surface of the first conductor layer 12 is exposed without beingcompletely etched.

Thereafter, the mask 19 that is made of the solder plating film can bekept and used as a bonding material. However, it is also possible that,instead of the solder plating film, a normal resist film is used as themask 19, and the mask 19 is removed after the formation of the metalposts 13. FIG. 6J illustrates an example of a structure in which themask 19 is removed.

As described above, the metal posts 13 can be formed to have variousshapes depending on a shape of the mask 19. However, in all of theembodiments illustrated in FIG. 1-3, the width (w1) of the metal posts13 is larger than the width (w2) of the connecting portions (12 b) ofthe wirings (12 a). That is, as described above, by making the width ofthe metal posts 13 larger, even for narrow wirings arranged at a finepitch, the connecting portions that connect to an electronic componentor the like can be ensured.

Next, when an electronic component is mounted, to protect the surface ofthe resin insulating layer 11, the solder resist layer 16 is formed onportions other than the connecting portions (12 b) of the wirings (12 a)on which the electronic component is mounted, and on the second surface(11 b) of the resin insulating layer 11, and the structures illustratedin FIG. 1-3 are obtained. The solder resist layer 16 is formed, forexample, by allying a solder resist over the entire surface andpatterning using a photolithography technique.

Thereafter, although not illustrated in the drawings, exposed surfacesof the metal posts 13 and the second conductor layer 12 are subjected toa surface treatment using coatings such as OSP, Ni/Au, Ni/Pd/Au, and Sn.

As described above, according to the present embodiment, the printedwiring board 1 having the metal posts 13 that project from the surface(first surface) of the resin insulating layer 11 is manufactured. Thewirings (12 a) of the first conductor layer 12 are electricallyconnected to an electronic component (not illustrated in the drawings)via the metal posts 13. Even when warpage repeatedly occurs in theprinted wiring board 1, the metal posts 13 can relax a stress that isdue to the warpage and acts on the printed wiring board 1. Therefore,the connecting portions between the electronic component and the wirings(12 a) of the first conductor layer 12 are unlikely to break and aconnection failure is unlikely to occur.

On the other hand, as is clear from the above-described manufacturingmethod, the metal posts 13 are formed by only patterning the metal film(13 a) that is formed on the surface of the carrier copper foil (18 b).Even in a printed wiring board in which the metal posts 13 are notprovided, the metal film (13 a) may be required as a base layer forforming the first conductor layer 12 and completely removed. In theabove embodiment, it is preferable that the metal film (13 a) be usedthat is slightly thicker than a metal film that is removed by etching.However, by just allowing a portion to remain, a thermal stress due toheat cycles during use can be relaxed. In other words, although only apatterning process is added, without requiring any additional material,an innovative effect is achieved.

Further, according to the manufacturing method of the above embodiment,the metal posts 13 are formed by patterning the metal film (13 a).Therefore, during the formation of the mask for the patterning, the sizeof the metal posts 13 can be adjusted. Therefore, even in a case where,for example, when an electronic component is mounted, warpage occurs inthe resin insulating layer 11 and differences in spacing occur betweenelectrode pads of the electronic component and patterns of the wirings(12 a) of the first conductor layer 12, this trend can be predicted inadvance. Therefore, a metal post 13 of a wiring (12 a) in a portionwhere the spacing is wide can be patterned to have a small diameter anda metal post 13 of a wiring (12 a) in a portion where the spacing thenarrow can be patterned to have a large diameter. By doing so, when anelectronic component is mounted, even when a solder reflow temperaturerises so that warpage occurs in the resin insulating layer 11, all ofthe electrode pads can be surely connected. Further, according to thepresent embodiment, the barrier metal layer 17 is provided on the lowerside of the metal posts 13. Therefore, for any shape that the metalposts 13 may be formed to have, the first conductor layer 12 is notetched and is not damaged.

In the embodiments illustrated in FIG. 1-3, the printed wiring board isillustrated having a two-layer structure in which a pair of conductorlayers (the first conductor layer 12 and the second conductor layer 14)are formed across the single-layer resin insulating layer. However, itis also possible that, for example, after the second conductor layer 14illustrated in FIG. 6F is formed, a second resin insulating layer and asecond metal foil are further laminated on the exposed surfaces of thesecond conductor layer 14 and the resin insulating layer 11 in a mannerillustrated in FIG. 6E, and thereafter the process of FIG. 6G andsubsequent processes are performed, thereby forming a printed wiringboard having a three-layer structure.

In a printed wiring board, a surface of a place other than where anelectronic component is mounted may be protected by forming a solderresist layer in the place. However, in a case where a circuit pattern isembedded on one side of an insulating substrate and a circuit pattern isformed on a surface, rather than being embedded, on the other side ofthe insulating substrate, a thickness of the solder resist layer on theone side is thinner than a thickness of the solder resist layer on theother side by an amount corresponding to a thickness of the circuitpattern. When volumes of the solder resist layers that are formed on theupper and lower surfaces of the insulating substrate are different,warpage occurs in the insulating substrate due to rise and fall oftemperature. There is a problem that, in the case where warpage occurs,for example, when an electronic component is mounted using solder bumps,a difference in height occurs between electrode pads of the electroniccomponent and pads of the circuit pattern that is embedded in theinsulating substrate, causing a connection failure to occur, or, peelingoccurs in the connection between the electronic component and thecircuit pattern because of heat cycles in which rise and fall of thetemperature are repeated due to operation and non-operation after theprinted wiring board is incorporated in a product, and thus thereliability is reduced.

A printed wiring board according to an embodiment of the presentinvention has a structure in which, even when wirings are thin and aninterval between the wirings is narrow due to advancement in highdensity and high integration, adhesion of the wirings is improved, andan electronic component or the like is reliably connected and a contactincident between adjacent wirings is unlikely to occur, and anotherembodiment of the present invention is a method for manufacturing such aprinted wiring board.

A printed wiring board according to another embodiment of the presentinvention has a structure in which, even when rise and fall oftemperature are repeated in an in-use state after the printed wiringboard is incorporated in a device, a thermal stress due to a differencein thermal expansion coefficient between an electronic component and theprinted wiring board can be absorbed, and another embodiment of thepresent invention is a method for manufacturing such a printed wiringboard. A printed wiring board according to one embodiment of the presentinvention includes: a resin insulating layer that has a first surfaceand a second surface that is on an opposite side of the first surface; afirst conductor layer that is embedded on the first surface side of theresin insulating layer and includes connecting portions to which anelectronic component is electrically connected; a second conductor layerthat is formed projecting from the second surface of the resininsulating layer; a via conductor that is provided to penetrate throughthe resin insulating layer and electrically connects the first conductorlayer and the second conductor layer; and a solder resist layer that isformed on the first surface of the resin insulating layer and on thefirst conductor layer and has an opening for exposing the connectingportions. Metal posts are respectively provided via a barrier metallayer on the connecting portions that are exposed from the opening. Themetal posts are formed such that the metal posts have a width largerthan a width of the connecting portions. The barrier metal layer isformed of a metal different from that of the metal posts and that of thefirst conductor layer, and is formed projecting from the first surfaceof the resin insulating layer.

A method for manufacturing a printed wiring board according to oneembodiment of the present invention includes: providing a metal film ona carrier that has a carrier metal; forming a barrier metal layer on themetal film over an entire surface, the barrier metal layer being formedof a metal different from the metal film; forming a first conductorlayer on the barrier metal layer, the first conductor layer being formedof a metal different from that of the barrier metal layer and includingmultiple connecting portions to which an electronic component isconnected; forming a resin insulating layer on the metal film such thatthe first conductor layer is embedded therein; forming a through holethat penetrates through the resin insulating layer from an exposedsurface side of the resin insulating layer to expose the first conductorlayer; filling the through hole with a conductor and forming a secondconductor layer the exposed surface side of the resin insulating layer;removing the carrier to expose one surface of the metal film; allowing aportion of the metal film to remain and etching the other portion of themetal film such that metal posts are respectively formed on theconnecting portions, the metal posts having a width larger than a widthof the connecting portions; removing, by etching, the barrier metallayer except a portion surrounding the metal posts, the barrier metallayer being exposed by the etching of the metal film; and forming asolder resist layer on the first surface side of the resin insulatinglayer, the solder resist layer having an opening such that the metalposts are exposed.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A printed wiring board, comprising: a resininsulating layer; a first conductor layer embedded into a first surfaceof the resin insulating layer and comprising a plurality of connectingportions positioned to connect an electronic component; a secondconductor layer projecting from a second surface of the resin insulatinglayer on an opposite side of the resin insulating layer with respect tothe first surface; a solder resist layer formed on the first surface ofthe resin insulating layer such that the solder resist layer is coveringthe first conductor layer and has an opening structure exposing theplurality of connecting portions of the first conductor layer; a barriermetal layer formed on the plurality of connecting portions of the firstconductor layer such that the barrier layer is projecting from the firstsurface of the resin insulating layer; and a plurality of metal postsformed on the barrier layer such that the plurality of metal posts ispositioned on the plurality of connecting portions of the firstconductor layer, respectively, wherein the plurality of metal posts isformed such that each of the metal posts has a width which is greaterthan a width of a respective one of the connecting portions, and thebarrier metal layer comprises a metal material which is different from ametal material forming the metal posts and a metal material forming thefirst conductor layer.
 2. The printed wiring board according to claim 1,further comprising: a via conductor penetrating through the resininsulating layer such that the via conductor is connecting the firstconductor layer and the second conductor layer.
 3. The printed wiringboard according to claim 1, wherein each of the metal posts has a firstend portion in contact with a respective one of the connecting portionssuch that the first end portion has a width which is greater than awidth of a second end portion on an opposite end.
 4. The printed wiringboard according to claim 3, wherein each of the metal posts has a curvedside surface curving from the first end portion to the second endportion.
 5. The printed wiring board according to claim 1, wherein eachof the metal posts has a first end portion in contact with a respectiveone of the connecting portions, and the barrier metal layer is formedsuch that the barrier metal layer comprises a plurality of portions eachhaving a surface area which is larger than a contact surface area of arespective one of the metal posts at the first end portion.
 6. Theprinted wiring board according to claim 1, wherein each of the metalposts has a first end portion in contact with a respective one of theconnecting portions, and the barrier metal layer is formed such that thebarrier metal layer consisting of a plurality of portions each having asurface area which is equal to a contact surface area of a respectiveone of the metal posts at the first end portion.
 7. The printed wiringboard according to claim 1, wherein the metal material forming theplurality of metal posts comprises copper, and the metal material of thebarrier metal layer comprises one of nickel and titanium.
 8. The printedwiring board according to claim 1, wherein the plurality of metal postscomprise a plurality of metal foil portions, respectively, and the firstconductor layer comprises a plated metal film layer.
 9. The printedwiring board according to claim 1, wherein each of the metal posts has aheight which is greater than a thickness of the solder resist layer. 10.The printed wiring board according to claim 1, wherein each of the metalposts has a thickness of 10 μm or greater.
 11. The printed wiring boardaccording to claim 1, wherein the opening structure of the solder resistlayer comprises an opening portion exposing the plurality of theconnecting portions of the first conductor layer.
 12. The printed wiringboard according to claim 1, wherein the opening structure of the solderresist layer comprises a plurality of opening portions exposing theplurality of the connecting portions of the first conductor layer,respectively.
 13. The printed wiring board according to claim 2, whereineach of the metal posts has a first end portion in contact with arespective one of the connecting portions such that the first endportion has a width which is greater than a width of a second endportion on an opposite end.
 14. The printed wiring board according toclaim 13, wherein each of the metal posts has a curved side surfacecurving from the first end portion to the second end portion.
 15. Amethod for manufacturing a printed wiring board, comprising: laminatinga metal film on a carrier comprising a carrier metal layer such that themetal film is laminated on a surface of the carrier metal layer; forminga barrier metal layer on an entire surface of the metal film such thatthe barrier metal layer comprises a metal material which is differentfrom a metal material forming the metal film; forming a first conductorlayer on the barrier metal layer such that the first conductor layercomprises a metal material which is different from the metal materialforming the barrier metal layer and includes a plurality of connectingportions positioned to connect an electronic component; forming a resininsulating layer on the first conductor layer such that the firstconductor layer is embedded into a first surface of the resin insulatinglayer; forming a second conductor layer on a second surface of the resininsulating layer on an opposite side of the resin insulating layer withrespect to the first layer; removing the carrier from the metal filmsuch that a surface of the metal film is exposed; etching the metal filmsuch that a plurality of metal posts is formed on the connectingportions of the first conductor layer, respectively, and each of themetal posts has a width which is greater than a width of a respectiveone of the connecting portions; etching the barrier metal layer suchthat the barrier metal layer comprises a plurality of portions formedbetween the metal posts and the connecting portions, respectively; andforming a solder resist layer on the first surface of the resininsulating layer such that the solder resist layer covers the firstconductor layer and has an opening structure exposing the plurality ofmetal posts.
 16. The method for manufacturing a printed wiring boardaccording to claim 15, wherein the forming of the second conductor layercomprises forming a through hole penetrating through the resininsulating layer and reaching the first conductor layer, filling aconductor material into the through hole and forming a second conductorlayer on the second surface of the resin insulating layer such that avia conductor connecting the first conductor layer and the secondconductor layer is formed through the resin insulating layer.
 17. Themethod for manufacturing a printed wiring board according to claim 15,further comprising: forming a metal coating on the barrier metal layer,wherein the forming of the barrier metal layer compriseselectrolytically plating the metal material of the barrier metal layeron the entire surface of the metal film, and the forming of the firstconductor layer comprises electrolytically plating the metal material ofthe first conductor layer on the metal coating.
 18. The method formanufacturing a printed wiring board according to claim 15, wherein themetal material forming the plurality of metal posts comprises copper,and the metal material of the barrier metal layer comprises one ofnickel and titanium.
 19. The method for manufacturing a printed wiringboard according to claim 15, wherein the metal film comprises a metalfoil such that the plurality of metal posts comprise a plurality ofmetal foil portions, respectively, and the first conductor layercomprises a plated metal film layer.
 20. The method for manufacturing aprinted wiring board according to claim 15, wherein the forming to themetal posts comprises forming the metal posts such that each of themetal posts has a thickness of 10 μm or greater.